She put a straw in that, Andy. Use it. That is citric acid and as you age the lifetime accumulation of such on your teeth gets ugly.
A straw keeps it off your teeth as you swallow. Never ever swish acid around your mouth. That's OJ and sodapop of any kind (carbonic acid) both.
I have given up soda, but do drink juice, and so far my teeth are good, but I had flouride all my life, which I think helped, but I also know many people believe this is dangerous, but then again, everything is a little when out of balance.
No problem with drinking juice or soda, just use a straw and don't swish.
Or swish water immediately after to wash it off. It's a slow, insidious thing and you won't know you have the problem until you have the problem -- and it's then too late because it doesn't heal. it's forever.
A water swish is a small price to pay.